Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque

H, W = map(int, input().split())
s = [input() for i in range(H)]
Map = [[0]*W for i in range(H)]
num_b = 0
for i in range(H):
  for j in range(W):
    if s[i][j] == '#':
      num_b += 1
      Map[i][j] = -1

dxy = [(1, 0), (0, 1), (-1, 0), (0, -1)]
que = deque([[0, 0]])
Map[0][0] = 1
while que:
  x, y = que.popleft()
  for dx, dy in dxy:
    xx, yy = x + dx, y + dy
    if 0<=xx<H and 0<=yy<W and Map[xx][yy] == 0:
      Map[xx][yy] = Map[x][y] + 1
      if (xx, yy) == (H-1, W-1):
        print(H*W - Map[xx][yy] - num_b)
        quit()
      que.append([xx, yy])

print(-1)